Perpendicular magnetic recording (PMR) technology is incorporated in magnetic recording media to increase areal density. Generally, PMR media includes four functional building blocks: a soft magnetic underlayer (SUL), a seed layer, an intermediate layer and a magnetic recording layer (RL). An example of conventional PMR media is shown in FIG. 1. The medium comprises a stack of layers on a nonmagnetic substrate 120. Between the SUL 130 and the substrate 120 is an adhesion layer 125. Upon the SUL 130 is a single seed layer of nickel alloy 135. Overlying seed layer 135 is a series of intermediate layers 160. On top of the intermediate layers 160 is a magnetic recording layer 175 which is protected by a carbon overcoat 180.
Reduction of grain size distribution in the magnetic recording layer is important to obtain a small switching field distribution (SFD), which is necessary to improve signal-to-noise ratios (SNR) of the PMR media. Although nickel alloy seed layers are extensively used in current PMR media, such alloys have been found to develop a coarse grain structure. Due to their coarse grain structure, nickel alloy seed layers tend to produce large magnetic clusters and a wide grain size distribution in magnetic recording layers.
There thus remains a need for controlling the grain structure of the seed layer while maintaining its texture to achieve a narrow grain size distribution and to improve recording performance of PMR media.